There is a telephone number you can call to get the item category code which gives you the amount of duty. Remember that the VAT always comes last so say you have to pay 4% duty that is calculated first and the VAT of 17.5% put on the whole total after that. DO NOT FORGET, you get charged duty and VAT on the shipping costs as well, so add these to the value of the goods before doing the calculations. Yes RIP OFF Britain!!
I have just done some importing and had a horrible bill, I challenged it and the courier company had categorised it wrongly. The courier company then just paid the duty and VAT and sent me the bill, always worth double checking, I am now going through the process of getting it refunded. I will get you the telephone number tomorrow